1. Field of the Invention
The present invention generally relates to electrical waveform generators and, in particular, to such generators which produce an analog waveform output in response to sequences of digitally-represented values.
2. Statement of the Prior Art
Since the development of digital-to-analog converters, it has been possible to store electrical waveforms as digital information in the form of sequential amplitude values and to therefrom reproduce the electrical waveform so represented by sequentially coupling the digital amplitude values to a digital-to-analog converter. The various improvements that have been made in digital-to-analog converters have allowed and generally caused increased use of this technique for digitally storing and then reproducing an electrical waveform as an analog signal. The initial applications of this process were generally in the area of waveform display and measurement. However, as the circuitry for performing this technique underwent development, attempts were made at expanding the various applications due to the relatively great flexibility available in defining a waveform by its sequential amplitude values. Various improvements that have been made in the output circuitry are exemplified and explained by U.S. Pat. Nos. 3,621,228; 4,355,367; and 4,438,503. The waveform generators or synthesizers described by these patents operate directly in the sense of conditioning and converting digital information into a desired analog waveform. As is evident from the latter two of these patents, there has been increased emphasis on applying this general technique to various specific purposes such as the ones shown of generating audible and VOR waveforms. Interest in expanding the capabilities of this technique continues for the purpose of providing a flexible waveform generator which is useful for many applications.
Waveform generators themselves, have evolved from dedicated analog circuitry producing a limited number of defined functions such as sine waves, square waves, and the like, to the use of somewhat dedicated digital circuitry for producing somewhat variable functions. Such advanced instruments are exemplified by U.S. Pat. Nos. 3,922,536; 3,967,100; and 3,978,326. Such instruments have provided some flexibility by using circuitry which allows different waveforms to be defined. However, as the means for definition is still limited by the dedicated circuitry specified for this purpose, so too is the flexibility of the instrument.
Given the trends of development in the area of waveform generation techniques, it is apparent that there still exists a need for a highly flexible and adaptable waveform generator or synthesizer which may also be easily understood and applied by operators having various levels of training and capability.